[Lhs-biohacking] spectrophotometer?

[Tommaso Vannocci]

Hi,

I was thinking that sooner or later we'll need to build a spectrophotometer (I checked prices on ebay but it's too expensive for us, around £300 and don't know actually if they work properly). A spectrophotometer is used to measure the concentration of products in a solution (bacteria, DNA, etc) and it is going to be useful, for example, to standardise the quality of our competent cells.

There are not so many resources for a DIY one but I found some interesting links (check especially the last one, quite funny):

http://www.instructables.com/id/A-simple-DIY-spectrophotometer/?ALLSTEPS

http://sci-toys.com/scitoys/scitoys/light/spectrograph/spectrograph.html

http://openwetware.org/wiki/Citizen_Science/The_Urinomics_Project

Tom

[Tommaso Vannocci]

also this kickstarter is not bad:

http://www.kickstarter.com/projects/jywarren/public-lab-diy-spectrometry-kit

[simon rose]

We have some of the parts for some of these  already. I have a couple of phototransistors, (one is already connected up and has tape around the outside to cut out stray light)  in my box,  there are loads of LEDS in the hackspace one or two Arduino boards if you are free come in and we'll start building one

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[simon rose]

Actually, the phototransistors I have are, according to their specs, most sensitive in the green part of the spectrum so this might be a problem but we can probably work round this.

[Tommaso Vannocci]

Not free today, sorry but really happy to help building it in the future... though you'll have to teach me, I'm not an expert of electronics.

For monitoring bacteria cultures we'll need to record absorbances at 600 nm, I think it's the colour yellow.

For DNA it's a bit more complicated: we need something to detect at 260 nm, maybe not possible at the moment.

[simon rose]

260nm is well into the UV  dunno if they'll work at that short a wavelength. Have to read up on this

[Tommaso Vannocci]

link to a nice diagram of the absorbance at 650 nm for bacteria:

http://www.google.co.uk/imgres?num=10&hl=en&safe=off&biw=1217&bih=702&tbm=isch&tbnid=WcVp5VQaWoE_uM:&imgrefurl=http://amrita.vlab.co.in/%3Fsub%3D3%26brch%3D73%26sim%3D1105%26cnt%3D1&docid=JbBGQ2td86j6BM&imgurl=http://amrita.vlab.co.in/userfiles/1/image/bacterial%252520growth.png&w=942&h=562&ei=ElCIUO28B6zO0AXB34HYBA&zoom=1&iact=rc&dur=1&sig=106893441209257557958&sqi=2&page=1&tbnh=147&tbnw=262&start=0&ndsp=20&ved=1t:429,r:1,s:0,i:69&tx=492&ty=270

[Nigel Worsley]

> link to a nice diagram of the absorbance at 650 nm for bacteria

you wouldn't need a spectrometer for that, just a cheap 650nm LED and a suitably
linear photodetector. And a processor to do the calibration and tedious monitoring
of the absorption for several hours so that the result is ready when you get back
from the pub :)

Nigle

[Tommaso Vannocci]

Thanks for the input Nigel! 

Well, I'm not an expert in electronics therefore I do not know much about suitable photodetector but we need this instrument not to monitor bacterial growth for several hours. We need to measure with good accuracy the cell density on the spot and to distinguish clearly between a 0.6 and 0.8 Abs at 600 nm (or 650 nm if 600 is not possible). If I'm correct this requires some accuracy. In my experience also the most simple of the instruments that I used at work were based on this schematics:

[william...@gmail.com]

A guy in the space pointed us towards this:

http://myspectral.com/

An arduino spectrometer. They had a form on the website to apply to be a beta tester, so I applied.

[Martin Dittus]

Just happened across your discussion about making your own spectrometer.

Have you seen the design by the Public Laboratory? Here's the latest version of a really basic one:
http://publiclaboratory.org/notes/mathew/11-30-2012/final-fold-mini-spectrometer-print-files-and-instructions

Other designs are here:
http://publiclaboratory.org/tool/spectrometer

I have a contact at the public lab if you want to approach them for questions, happy to put you guys in touch.

m.

On 25 Oct 2012, at 21:06, william...@gmail.com wrote:

> A guy in the space pointed us towards this:
>
> http://myspectral.com/
>
> An arduino spectrometer. They had a form on the website to apply to be a beta tester, so I applied.
>
> On 25 October 2012 10:34, Tommaso Vannocci <ktom...@gmail.com> wrote:
> Thanks for the input Nigel!
> Well, I'm not an expert in electronics therefore I do not know much about suitable photodetector but we need this instrument not to monitor bacterial growth for several hours. We need to measure with good accuracy the cell density on the spot and to distinguish clearly between a 0.6 and 0.8 Abs at 600 nm (or 650 nm if 600 is not possible). If I'm correct this requires some accuracy. In my experience also the most simple of the instruments that I used at work were based on this schematics:

> <image.jpeg>

[Tommaso Vannocci]

Hi Martin, 

thanks for the offer. We have some peculiar requirements about wavelengths and such but we'd love to see what the Public Lab are up to. I noticed they have nice projects to test their spectrometer and I think it would be cool also for us to help them out with the testing. 

I'd like to speak about it more in details, are you around this wednesday?

Tom

[Martin Dittus]

Unfortunately I likely won't be there, and I'm also not the right person to talk to if you want to discuss their projects; I simply happen to have a contact there who we could use to find the creators of particular projects.

m.